Do Breathable Paints Help With Damp?

Paint is the last thing people think about with damp, but it can make a real difference, good or bad.

Why paint matters

Walls always contain some moisture and it needs to move. Older solid walls, lime plasters and walls drying out after a leak or damp treatment are constantly releasing moisture into the room. If you cover them with a finish that doesn’t let vapour through, that moisture gets trapped behind it. The result is blistering and peeling paint, salts pushing through, and plaster that stays damp longer than it should.

Breathable paints

Vapour-permeable paints let moisture pass through the paint film. The main types are:

• Mineral and silicate paints, which bond with mineral surfaces and are very breathable.
• Clay paints, often used on lime and clay plasters.
• Limewash, the traditional finish for lime-plastered and stone walls.
• Some modern emulsions marketed as breathable. Check the manufacturer’s information rather than relying on the label alone.

Paints that trap moisture

Vinyl emulsions, especially vinyl silk, along with oil-based paints, many masonry paints on solid walls and so-called damp-proof paints, can reduce vapour movement a lot. Painting a damp wall with a waterproof paint might hide the patch for a bit, but the moisture is still in the wall, and often it just moves sideways or up to where it can escape.

Where to use them

• Lime-plastered walls and older solid walls.
• Walls that have recently been replastered after damp work, where the plaster and masonry are still drying. Follow your contractor’s advice on how long to wait before decorating and what to use.
• External walls of older properties, where the wall needs to dry outwards.

In a modern house with cavity walls and gypsum plaster that’s dry and sound, standard emulsions are fine. The key is matching the finish to the wall.

Breathable paint isn’t a cure. If the wall is wet because of a leak, rain getting in or rising damp, fix that first.